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Shamrock Island
Eco Restoration Gypsum Dunes Shamrock Island


From the Winter '99, Volume 24, No. 3 Issue of Horizon
by Niki Frances Mc Daniel
Horizons Editor

Reprinted by permission of The Nature Conservancy of Texas, copyright 2000

For the birds: Partners conserve nesting grounds on beautiful Shamrock Island

Protected from the winds and waves of the Gulf of Mexico by Mustang Island, Shamrock Island Preserve in Corpus Christi Bay is a hurricane-created refuge that includes sand and shell beaches, inter-tidal wetlands, an interior seagrass lagoon and vegetated beach ridges.

Shamrock was a barrier spit before its connection to Mustang Island was severed during Hurricane Celia in 1971. The breaking of the land bridge limited predator access, allowing the island to become one of the most important colonial bird nesting islands on the Texas coast.

As many as 21 bird species, including the threatened reddish egret and white-faced ibis, nest on the 110-acre island. Gull-billed, Sandwich, Caspian and royal terns nest on the high-quality beach habitat; in some years, royal terns number close to 8,000, making Shamrock by far the most important nesting site for this species on the Texas coast. Black skimmers also use the shell beach sites, while the more vegetated shell-hash flats provide nesting habitat for up to 6,000 laughing gulls. On the beach ridges vegetated by salt cedar, nesting species include great blue herons, little blue herons, tricolored herons, black-crowned night herons, great egrets, snowy egrets, reddish egrets, white-faced ibis and roseate spoonbills. The sooty tern, which nests only rarely in Texas, also nests at Shamrock Island.

Through a partnership developed with the Texas General Land Office in 1995, The Nature Conservancy of Texas acquired Shamrock Island and now manages it as a preserve. Another important partner is the present oil and gas operator on the island, Bristol Resources Corporation. Together, Bristol and the Conservancy cleaned up and restored a portion of the island damaged by past oil and gas extraction. Bristol Resources also installed a docking facility, where the Conservancy keeps the Miss Shamrock, a 17-foot boat essential for island access and research as well as for patrolling, protecting and maintaining the island preserve.

However, the work of preserving Shamrock Island is far from complete. A recent study showed that the island was rapidly losing ground to erosion. Vulnerable to winter northers, the northwest shoreline lost 515 feet between 1956 and 1995. This erosion also threatens to breach the island, which could degrade the interior lagoon and result in the loss of valuable bird habitat. Moreover, if this process continues, crucial seagrasses will be unprotected from bay currents, and the increasing turbidity could damage seagrass habitat or cause it to disappear altogether. Protecting seagrass beds is imperative: Texas coastal wetlands serve as nursery grounds for more than 95 percent of the recreational and commercial fish species found in the Gulf of Mexico.

To address the island's rapidly eroding northwestern boundaries, a joint shoreline restoration project was mounted by The Nature Conservancy with a host of partners, including the Texas General Land Office, Texas Parks and Wildlife Department, the Coastal Bend Bays Foundation, Texas Audubon Society and private businesses and individuals.  Completed in February 1999, this project successfully installed a sand-filled "geotube" of heavy synthetic cloth -- 4,600 feet long and five feet in diameter -- to brace the north and west sides of the island.

In addition, 90,000 cubic yards of sand were pumped from the island's submerged neck and spread along 650 feet of the northwest shore to create a "feeder beach" - so called because this supply of sand will replenish the shoreline along the southern portion of the island. Without this shoreline stabilization, the island would continue eroding unabated.

Still more work remains to be done, according to Jim Bergan, South Texas Program Manager and overseer of the island's erosion and restoration project, noting plans for a series of volunteer events on the island to plant cordgrass to create a marsh area for additional protection against erosion on the island's northwest side. To prepare for the planting, a five-acre area between the shore and geotube has been filled with 10,000 cubic yards of sand. To avoid disturbing nest birds, the marsh creation project is being carried out during the non-nesting season between September, 1999 and February 15, 2000. Further planting will continue in September, 2000.

The Nature Conservancy of Texas has initiated various outreach and education programs involving Shamrock Island. Local high school and grade school science classes have conducted projects on the island, while teacher workshops and Elderhostel projects have used the island preserve as a living laboratory.

Besides reducing erosion, the project will protect and restore island and wetland habitat for nesting birds, including several endangered and threatened species. In addition, restored seagrass beds will benefit the local economy, where sport fishing currently nets $83 million and birdwatching brings in $4.6 million annually. The project will also enhance water quality in Corpus Christi Bay, trapping residual seepage of hydrocarbons from oil and gas operations in vegetation that naturally converts this potentially toxic material into less harmful forms.

Finally, this project will provide a valuable model for other wetland protection and restoration efforts by the U.S. Fish and Wildlife Service, the Texas Parks & Wildlife Department, the Texas General Land Office, the Corpus Christi Bay National Estuary Program, and other public and private groups in the Corpus Christi Bay area.


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